1. Field of the Invention
This invention relates to suspended particle accelerometers that are primarly used in inertial navigation systems.
2. Background of the Invention
Accelerometers and rate sensors are key components in the control systems used in missiles, aircraft, ships, space vehicles, and other devices that must be maintained in a stabilized and controlled altitude and orientation relative to their surroundings. They are also used in navigation systems where the vehicle or device is required to accurately move from one point in space to some new desired point. The purpose of an accelerometer is to accurately determine forces acting on a body. This information can then be used as input to guidance and navigation systems either to counteract the applied forces or to predict the future state vector of the device.
There are a wide number of accelerometers available on the market. Many of these accelerometers employ principles of mass and spring action in an acceleration environment. In these types of accelerometers, a mass is moved from a null position whenever a force is detected parallel to the prime or active axis of the accelerometer. Some devices may use piezoelectric effects or changes in period of an oscillating element.
Other accelerometers employ a suspended particle. For example, the particle can be suspended by a properly shaped electrostatic field in a stable position whereby the forces acting on the particle are exactly balanced by the field. Accelerometers using this principle are disclosed in U.S. Pat. Nos. 3,370,472, 3,206,987, 3,664,196, 3,965,753, 4,384,487, 4,583,404, 4,566,328, and 4,688,141.
An inherent problem with prior art electrostatic accelerometers is their inability accurately to detect relative movement of the particle relative to the field plate.
The instant invention has overcome many of the disadvantages of the prior art devices by providing means for detecting movement of the charged particle from the null position.
Additional advantages of the invention are set forth in part in the description that follows, and, in part, will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims.